This video documents an unprecedented series of experiments investigating the reactions between the two most reactive elements on Earth: fluorine and cesium, alongside their highly reactive interhalogen compounds (bromine trifluoride and chlorine trifluoride). Conducted in a specialized laboratory at Philips University Marburg with Professor Dr. Krauss, the experiments involved liquefying fluorine at -196°C in custom PFA containers and carefully handling air-sensitive liquid cesium within an argon glove box. A custom-made stainless steel mechanism was designed to safely dispense liquid cesium from a distance. The experiments revealed extreme reactivity, with cesium igniting upon air exposure or reacting with PFA caps. Reactions with bromine trifluoride and chlorine trifluoride were violent, often occurring in the gas phase or with delayed explosions, sometimes ripping the reaction tubes. The climactic reaction between liquid fluorine and cesium was incredibly volatile, with even fluorine vapor causing explosions that launched the containment tubes, preventing the cesium from fully reaching the liquid. The video showcases the challenges and dangers of working with these substances while capturing previously unseen chemical phenomena.
Summarizing the Reaction of Fluorine and Cesium: The World's Most Reactive Elements
0:03 The Most Reactive Elements: The video explores the reaction between Fluorine (F2), a highly reactive and toxic gas with the highest electronegativity, and Cesium (Cs), the most reactive metal with the lowest electronegativity.
0:38 Nuance in Reactivity: The creator clarifies that while fluorine can burn skin and cesium ignites in air, the exact conditions (concentration, pressure, humidity, temperature, surface area) determine the intensity of the reaction.
2:49 Unique Experiment: The core of the video is to react liquid fluorine with liquid cesium, a feat never before attempted, in addition to testing interhalogen compounds like bromine trifluoride (BrF3) and chlorine trifluoride (ClF3).
3:40 Expert Collaboration: The experiments were conducted at Professor Dr. Krauss's fluorine lab at Philips University Marburg, emphasizing the specialized knowledge and equipment required.
4:17 Liquid Fluorine Preparation: Fluorine gas is liquefied at -196°C in specially designed PFA (fluorinated polymer) containers, continuously cooled with liquid nitrogen. Warmed tubes would burst, releasing toxic gas.
7:19 Interhalogen Preparation (ClF3 & BrF3): Chlorine trifluoride (ClF3) is also condensed into PFA tubes using liquid nitrogen, while bromine trifluoride (BrF3), being liquid at room temperature, is directly filled into tubes.
9:22 Cesium Handling: Cesium is stored and handled in a sealed argon-filled glove box. It is liquefied with a heating band (melting point 28°C), poured, and drawn into syringes, with PFA caps sealing the tips to prevent air exposure.
11:10 Custom Dispensing Mechanism: A custom-made stainless steel mechanism (sponsored by PCB Way) was built to safely and rapidly push cesium out of syringes from a distance, as plastics would burn on contact with fluorine.
14:38 Cesium Incidents: During preparation, cesium accidentally ignited upon air exposure and reacted violently with the PFA caps when heated, turning them black where it touched.
Attempts to react liquid fluorine with cesium resulted in extremely violent explosions.
Even the vapor above the liquid fluorine caused such a strong reaction that the PFA tubes were launched away, preventing most of the cesium from reaching the liquid.
23:49 Innovative Solution: With no more cesium syringes, Professor Krauss proposes reacting fluorine with petroleum ether, followed by cesium, as a final experiment.
24:30 Acknowledgements: The video concludes with thanks to the team, including other YouTubers, film crew, PhD students, and Professor Krauss for making the unprecedented experiments possible, and invites suggestions for future fluorine experiments.